Permanent setting of wool and wool-containing articles

ABSTRACT

PERMANENT SET IS ESTABLISHED IN WOOL OR WOOL CONTAINING GARMENTS OR PIECES OR SUCH GARMENTS OR PIECES CONTAINING OTHER KERATIN FIBRES WHICH HAVE BEEN PREVIOUSLY PARTIALLY SET BY TREATING THE GARMENTS OR PIECES WITH UNSATURATED STEAM UNDER CONDITIONS OF PRESSURE, TEMPERATURE AND RELATIVE HUMIDITY AT WHICH THE RATE OF SETTING IS GREATER THAN THE RATE OF RELEASE OF SET.

United States Patent US. Cl. 8128 12 Claims ABSTRACT OF THE DISCLOSURE Permanent set is established in wool or wool containing garments or pieces or such garments or pieces containing other keratin fibres which have been previously partially set by treating the garments or pieces with unsaturated steam under conditions of pressure, temperature and relative humidity at which the rate of setting is greater than the rate of release of set.

This invention relates to the so-called permanent setting of garments or other articles made wholly or partly of wool or other keratin fibres. The term permanent setting is used relatively to mean that the setting is of such durability that it will withstand at least wetting and dry cleaning.

Various methods have been developed with the object of enabling durable creases or like effects to be imparted to wool garments. For instance, durable creases can be imparted to wool slacks by damping the crease area with a solution (approx. 12%) of a setting reagent, such as ammonium thioglycollate, sodium bisulphite, monoethanolamine or its sulphite, and then pressing each part of the garment for a cycle of 20-30 seconds steam plus 2030 seconds bake followed by vacuum for a few seconds. Such a process is described in Australian specification No. 225,996. Alternatively, the fabric can be pretreated with the setting reagent, and the required areas of the garment dampened with water before pressing as above or the fabric can be pretreated with, for ex ample, urea and diethanolamine carbonate (24%) and the garment of normal regain pressed for at least the above times. Such a process is described in Australian specification No. 281,525. Usually, only the legs are set because to set fully each part of the top would require a further pressing time of about 4 min. per garment.

These pressing times are considerably longer than those used (about 5 seconds) simply to form the shape of the garment and have been one of the impediments to wider adoption of durable creasing of wool slacks.

Procedures for producing so-called permanent-press efiects in all-wool garments are currently under development. In these procedures, the set is stabilized to withstand machine washing by an aftertreatment such as crosslinking with formaldehyde. Such a process is described in Australian specification No. 46845/ 68. Satisfactory permanent-press performance requires the level of setting to be even higher than that which is acceptable for durable creases (i.e. to withstand only wetting or dry cleaning). The set-stabilizing treatment could be conveniently performed in an oven in a similar way to cellulosic/ synthetic garments but, as before, the steam-pressing step could crease a serious bottleneck.

Various attempts to reduce the steam-pressing time by increasing the reagent concentration have been unsatisfactory because often the rate of damage increases more rapidly than the rate of setting. Attempts have been ice made to bring about permanent setting of untreated fabric by treating such with saturated steam under pressure in an autoclave. However, under these conditions, sharp creases are obtained only if they are held in formers during the treatment.

'An object of the present invention is toovercome the problem of undesirably long steam-pressing times in processes of the type used for the permanent setting of fabrics, garments or other articles made wholly or partly of wool. For convenience of description such articles will be referred to as wool articles.

With this objective in view, this invention provides a process for permanently setting wool articles in which the articles, which have been partially set in any suitable manner, are treated with unsaturated steam under conditions of pressure, temperature and relative humidity at which the rate of release of set is not greater than the rate of setting.

If a fabric containing, for example, sodium bisulphite is steam pressed for only a few seconds and then soaked in hot water or hung in saturated steam, the crease will fall out. However, it will not be released completely be cause setting is occurring during the steaming or soaking, and so the crease will be set in a partially released configuration. On the other hand, if the crease is hung in a dry oven, it will remain perfectly sharp but, in the ab sence of water, no setting will occur so that the crease will still fall out when wetted later. Of course, if the fabric is fully set by steam pressing for about 1 min. the crease will remain sharp after steaming or soaking. Therefore, it seems likely that a partially set crease would not fall out if hung in unsaturated steam. This realization forms the basis of the present invention.

The same molecular bond rearrangements are involved in setting and release of set, but the rates of setting and release would not be expected to be identical under the same conditions. It is known that a marked hysteresis is exhibited by wool in deformation/recovery phenomena, i.e., recovery is slower than deformation. A similar hysteresis is evident in setting and release of set. For example, a stretched fibre set by boiling in water for an hour is not fully released to its native length by boiling slack for an hour. A similar effect has also been observed with respect to temperature rather than time; set acquired at one temperature is not fully released until the temperature is approximately 2040 C. higher. A similar hysteresis might also exist with respect to relative humidity or, rather, regain. In that case, and this is a further important feature of the invention, steam could be used at a temperature and r.h. less than at which the rate of increase of set is less than the rate of setting, or even under such conditions of temperature and relative humidity that the rate of release is negligible but the rate of setting is still appreciable.

Based on these considerations, a specific embodiment of the invention for the production of a durable crease in a wool article comprises the steps of steam pressing a formed crease in the article for a short time, say 5-10 seconds, and then exposing the article to unsaturated steam under conditions of temperature and relative humidity such as will complete the setting without any substantial decrease of the sharpness of the crease.

Temperature and regain of the wool are the most important parameters in determining the correct conditions for the method; relative humidity (r.h.) is important only insofar as it affects regain although of course, it is more easily determined. However, it is difficult to specify precisely optimum conditions precisely because of the difi'iculties of making meaningful measurements of temperature and especially relative humidity (more especially regain) under the conditions of operation of the method, i.e. usually in a steam oven. Thus, usually, a trial and error approach to determine the optimum conditions will be necessary.

In general terms, however, it can be stated that the regain of the wool is approximately within the limits corresponding to those obtained when wool is exposed to from 80% to 95% r.h. in steam at atmospheric pressure; these r.h. values correspond to raising steam saturated at 100 C. to 106.5 C. and 101.5 C. respectively.

The preferred procedure is to heat the wool to above the required temperature, e.g. in an oven, introduce steam, and allow the temperature to fall to that corresponding with the required r.h. and hold for the required time. The range of r.h. covered during the cycle is then wider than above, but during a critical period must be within those limits, preferably starting at the low r.h. end and gradually approaching the high r.h. end during the critical period.

The exact time, temperature, and r.h. range are greatly influenced by the size of the oven and the amount of wool it contains and so it is not possible to specify exactly the conditions. In full scale operation, the times required to reach thermal equilibrium are very much greater than in the laboratory. The exact conditions must be determined during operation of the plant by including experimental fabrics in a fully loaded oven and measuring, as in the tables in the specification, the degree of crease opening and degree of set to determine the upper and lower limits of r.h. or the rate at which the critical region is approached and passed through.

The following procedure illustrates one approach to the method using an oven at atmospheric pressure: the temperature of the oven containing the creased, partially set wool is raised to 110 C. during up to 30 minutes so that the regain drops below and saturated steam at atmospheric pressure is introduced (with or without turning off the source of heat). The temperature then drops and can be allowed to reach approximately 105 C. (i.e. r.h. slightly greater than 80%) as rapidly as desired, consistent with uniform displacement of air by steam. The temperature can then be held around this value or, preferably, slowly taken through the critical r.h. range to approximately 102 C. (i.e. approximately 95% r.h.) during about 15 minutes. (More precisely the wool should be taken through the critical regain range during this time. The actual time in practice will depend on how quickly the dry wool takes up moisture to reach the lower limit of the regain range after the oven has reached the required r.h. The total time taken for this stage can be as much as minutes.) The time spent in the critical range and whether the rate of going through it is uniform will depend on the initial degree of setting of the wool on the steam press, whether it has been modified in any way, e.g. by shrink-proofing, and whether it contains a setting agent such as bisulphite. The last two would allow the time to be shortened, but in most cases thermal lag in a large oven would be the limiting factor.

After the wool has been in the critical region (or the correct part of it) for an adequate time to acquire sumcient set without losing any crease sharpness, the wool can then be removed or, alternatively, the steam can then be allowed to become saturated, i.e. the temperature dropped to 100 C. (at atmospheric pressure), if, for example, it is required to produce permanent press eifects as disclosed in co-pending application No. 63436/ 69.

The basis and practice of the method of the invention is illustrated by the following examples. It should be noted however, that the invention is not limited thereby.

EXAMPLE 1 This example shows that setting can be completed by 4 their centres and given a partial setting treatment. Details of the treatment used are as follows:

Shrinkresist.-Acid chlorination followed by treatment with a 1% solution of potassium bromite in saturated salt.

Partial set.'Pad on 2% NaHSO dry, steam press 10 seconds; condition to 65% r.h.

Full set.Pad on 1% tNaHSO dry, damp with water, steam press wet for 30 seconds steam-{-30 seconds bake.

The partially set strips were hung by one arm of the crease in sealed glass tubes containing the calculated quantity of water required to maintain the r.h. at the values shown in Table 1 and the tubes were heated for a total of 30 minutes, including heat-up time. No allowance was made for the decrease in regain with increase in temperature because adequate data was not available for such temperatures. Consequently, during heating, the r.h. was probably higher and the regain lower than the nominal values.

After cooling and removal of the strips from the tubes, crease angles were determined as the mean of 5 measure ments on yarn snippets from crease (each arm approximately 10 mm. long) after soaking in water at 20 C. for /1. hour.

The conditions and results are set out in Table 1.

TABLE 1 Heating Crease Rh, Temp, angle Pretreatment percent 0. degrees Untreated, partially set 65 94 Shrinkresist, partially set- 65 110 71 Shrinkresist, partially set 60 Untreated, partially set--. 59 Shnnlrresist, partially set 52 Untreated, fully set 45 Shrinlaesist, fully set 47 EXAMPLE 2 In this example experiments were carried out at atmospheric pressure. The samples were first heated in an air oven in order to avoid condensation of water on the fabric on the introduction of the steam. After being preheated, the fabric was exposed to superheated steam under the conditions set out below.

Fabric samples 20 cm. x 20 cm. of medium weight grey, worsted serge were pretreated as in Example 1 and provided with a partiallyset crease down the centre. The samples were hung in an oven with both arms of the crease clamped at the top about 2 cm. away from the crease line. The temperature was raised to 105 C, and steam was introduced. The wet-bulb temperature rose to 100 C. and during about 5 minutes, the dry-bulb temperature dropped to 101-102 (1.; the latter was maintained around 101 C. for a further 10 min.

In these experiments, the larger pieces of heavier fabric were used to simulate the way in which the legs of a pair of slacks might hang. This fabric is a little more difiicult to set than the lightweight undyed fabric of Example 1.

The conditions and results are set out in Table I. Set is expressed as (l80-release angle)/(180-set angle), and was measured on yarn snippets taken from the bottom of the crease.

The results show that under the conditions specified there was hardly any loss of crease sharpness during heating.

The crease sharpness of the fully set control immediately after pressing was of course greater because it was pressed in the wet state and, consequently, it was also sharper after release. However, when the degree of set is calculated as indicated in Table 2, it can be seen that adequate setting occurred during the heating cycle.

The above description and experimental results indicate that the process of the invention could be usefully applied in order to reduce the steam-pressing times which are at present required in durable creasing treatments. The invention could, however, be of even greater importance in processes for producing permanent-press effects in wool and wool-containing articles because of the possibility of carrying out one or more set-stabilizing steps in the same chamber as that in which the steam treatment for completion of the setting is performed.

We claim:

1. A method for permanently setting a wool article, comprising the steps of: (a) contacting the partially set article with unsaturated steam under conditions of temperature and pressure equivalent in effect on wool regain to steam at atmospheric pressure at or above 106.5 (3.; (b) maintaining the article in contact with the steam while allowing the temperature to fall to a value at which the steam is equivalent in effect on wool regain to steam at atmospheric pressure and a temperature of from l01.5 to 106.5 C.; and (c) holding the temperature at said value for a period sufiicient to bring about permanent setting of the article.

2. A method as claimed in claim 1, wherein, prior to step (a), the article is heated to a temperature above that first stated in step (a); and in step (b) the temperature is allowed to fall to a value corresponding to the upper limit of said range; and in lieu of step (c), the

temperature is allowed to fall further to a value corresponding to the lower limit of said range during a period sufficient to bring about permanent setting of the article.

3. A method as claimed in claim 1, wherein in step (a) the relative humidity is equivalent to r.h. at atmospheric pressure, and in step *(b) the relative humidity is equivalent to a value between 80 and r.h. at atmospheric pressure.

4. A method as claimed in claim 1, wherein the conditions are chosen so that the wool regain is between 15% and 25% during the steam treatment.

5. A method as claimed in claim 1 wherein the said period is from 15 to 30 minutes.

6. A method as claimed in claim 1 wherein the heating and steam-contacting steps are carried out in a chamber.

7. A method as claimed in claim 1 wherein the process is carried out at or near atmospheric pressure.

8. A method as claimed in claim 1, wherein the wool comprising the article has been subjected to a shrinkresist treatment.

9. A method as claimed in claim 1 wherein the wool article is first subjected to a partial setting treatment involving steaming and/or steam pressing for 5 to 10 seconds.

10. A method as claimed in claim 1, wherein the partial setting treatment involves the application to the wool of a setting agent.

11. A method as claimed in claim 10, wherein the setting agent is sodium bisulphite.

12. A method as claimed in claim 2 wherein the relative humidity at the said upper temperature limit is equivalent to 80% r.h. at atmospheric pressure, and the relative humidity at said lower temperature limit is equivalent to 95% r.h. at atmospheric pressure.

References Cited UNITED STATES PATENTS 3,059,990 10/1962 Koenig et a1 8-128 3,423,166 1/1969 Peters 8-128 GEORGE F. LESMES, Primary Examiner T. J. HERBERT, 1a., Assistant Examiner 

